The demand for bandwidth is increasing with more and more devices accessing data networks such as the internet. Current device designs and associated applications are directed to achieve higher operating bandwidths. Bandwidth requirements are increasing because more wireless connections between electronic devices are required as the consumers require remote access to the Internet with their cell phones to retrieve large amounts of data, watch real time video content such as watching live sports on their cell phones, etc.
An important aspect of high speed electronic devices actually resides in the design of connections between electronic components, whether the connection is being made via a cable or through printed circuit board traces. Currently, true high bandwidth communication is achieved with optics in order to avoid or reduce noise and signal degradation that can be introduced with electrical interconnects. Large optical networks connect metropolitan areas electronically. For distances in the thousands of miles, an optical connection is perfectly justified; however, now devices must be able to transfer high rates of data between resident components, e.g., as with components resident on a single printed circuit board (PCB) within an electronic system. Within an electronic communication system, for example, electronic components are basically silicon installed onto PC boards and communicate along traces formed on or within a single PCB or through electrical connectors coupling components that are not co-located on the same PCB. Even transferring data short distances, such as millimeters to inches apart, component designers believe that optical connections may be best because optical data transfer can be achieved at very high data-rates.
Optical connections are perhaps the most effective way to transfer data; however, optical interconnect systems are more expensive than electrically-based systems. The present inventor believes that optical connections will continue to be used and have their place; however, many applications do not require such costly and elaborate designs. Where inter-system communication between components is involved, optical connectivity and its associated expense is not justified. High bandwidth can be achieved using the teaching of the present invention.
Currently, signals travel along copper traces in/on a PC board. Signals driven from a transmitter of a silicon-based component to the receiving component associated with another silicon substrate. The highest speed non-optical connector currently in use can probably achieve 15-20 gigabits. Higher transfer rates are not obtainable given the current connector designs because pin-and-socket connection geometries are inherently “resonating structures.”
Pin-and-socket connectors are basically a male connector and a female mating part. The male connector has a protruding copper pin; the female connector has a socket which is used to receive the pin. The problem is that such geometry is an inherent resonating structure. This design forms, within the connector, a microwave cavity, which is a resonating geometry. A resonance circuit has a very high Q (“Q” is the quality of the resonance). A very high Q results in a very strong resonance with very little power, creating a low-loss circuit. Although a passive circuit, it has a very strong resonance because it has a very well defined resonance frequency. The typical connector pin and socket geometry can start to resonate at 10-20 gigahertz, which presents a problem. The resonance circuit has a specific frequency. When a broadband signal is driven into that circuit, it excites the resonance of the circuit. If the desire is to drive a signal of any other frequency than is related to the resonating frequency, the connection design basically “filters out” the out-of-band signal. Thus no other signal except for that resonating signal can be effectively transmitted.
When driving a circuit having a geometry that can resonate at a particular frequency with a variety of frequency signals into the resonating circuit, no other signal can usually sustain itself except for the signal associated with resonating frequency provided by the circuit's geometry. All the other frequencies may be suppressed except for those in the resonating frequency range. This is a problem where hardware designs or assembly mistakes cause the circuit to resonate. Ideally, the path where data is transmitted from point A (or circuit A) to point B (or circuit B) should not be a resonating circuit (with resonance determined by the physical properties of the interconnects) because broadband data signal is usually transmitted across this path. Resonating interconnect is of limited use if it resonates when signals are driven into it, and it will only pass through a certain frequency of signal and will suppress all other frequencies because of circuit resonance. Circuit resonance is the problem with the inherent geometries of the pin and socket connector and mating PCB designs.
Some connectors comprise through-hole device installation into the PC Board, which is where one side of the PCB has a socket for the connector to mate with (the mating part) and the other side has a small, sharp-edged metal pin that extends out through the back of the PCB and creates a metal stub. The metal stub is associated with a component, is passed through the PCB socket and facilitates soldering of components to traces or sockets at the back side of PCBs. The stub is physically secured by solder on one side (typically the back side) of a PCB, but is electrically “floating”. That floating end of the stub is not connected to anything on the board and is merely floating from an electrical standpoint. A floating piece of metal will also resonate at high frequencies. Resonance is not desired because it can suppress other frequencies except for the resonating frequency. A resonant circuit can act similar to a filter and attenuate/suppress all signals outside of the resonant frequency band and can introduce noise.
Another problem exists where PCBs and connectors are made of a plastic shell or the like. Today a dielectric material like plastic or FR-4 is typically used for connectors and PCBs. FR-4 stands for Fire Retardant Type 4 so it is a safety material. FR4 is inexpensive; however, the problem with FR-4 and other plastic materials is that as frequencies increase to microwave levels, plastic and FR4 start to become energy absorbers. FR4 dissipates energy in the form of heat which causes electrical energy to convert into thermal energy. Where radio frequency components are involved in a connection (either via PCB or connector), the dielectric material will heat up proportionally to the increases in frequency into multi-gigahertz range. The reason for the heat up is that the dielectric material is bombarded by microwave energy causing the molecular bonds (covalent bonds) to vibrate. FR4 and other Plastic material absorb microwave energy. The electrons in plastic or glass, e.g., such as in the dielectric material of a PCB, becomes excited and they absorb high frequency electromagnetic-field-generated energy. Plastic connector shells also heat up. As an electrical signal is passed through the pins in a connector, the electrical waves propagate between the signal pins within a plastic structural device typically associated with the pin receiver to prevent the pin from bending or shorting into the adjacent pin. The pin is captured by a plastic shell, which provides the mechanical structure and strength to the pin, also absorbs energy from the electrical signal carried by the pin. The transmission of high frequency signals on pins causes the plastic shell to heat up as it absorbs the energy.